The present application is based on and claims priority to Japanese Patent Application No. 11-170731, which was filed on Jun. 17, 1999, the entire contents of which are hereby expressly incorporated by reference. The entire contents of Japanese Patent Application No. 11-75968, which was filed on Mar. 19, 1999, is also hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to a control system for a personal watercraft. More particularly, the present invention relates to a emergency shut-off system for a personal watercraft.
2. Description of Related Art
As personal watercraft have become popular, they have become increasingly fast. Today, personal watercrafts are capable of speeds greater than 60 mph. To attain such speeds, personal watercrafts are driven by high power output motors.
Typically, two-cycle engines are used in personal watercraft because two-cycle engines have a fairly high power to weight ratio. One disadvantage of two-cycle engines, however, is that they produce relatively high emissions. In particular, large amounts of carbon monoxide and hydrocarbons are produced during operation of the engine. When steps are taken to reduce these emissions, other undesirable consequences typically result, such as an increase in the weight of the engine, the cost of manufacture, and/or the reduction of power.
It has been suggested that four-cycle engines replace two-cycle engines in personal watercraft. Four-cycle engines typically produce less hydrocarbon emissions than two-cycle engines while still producing a relatively high power output. However, adapting four-cycle engines for use in personal watercraft has its own engineering and technical challenges.
For example, as compared to two-cycle engines, four-cycle engines are typically more susceptible to water corrosion. Accordingly, personal watercraft with four-cycle engines typically include an emergency shut-off system that prevents water from entering the engine compartment when the personal watercraft is overturned. An example of such an emergency shut-off system is disclosed in Japanese Patent Laid Open No. 8-49596 (1996). This particular emergency shut-off system includes an overturn switch. The overturn switch includes a weight that sways back and forth as the personal watercraft is rocked from side to side. When the weight sways beyond a specified range, a circuit in the overturn switch is closed and the engine is shut off. Thus, the air pressure inside the engine compartment remains positive and water is less likely to be drawn into the engine compartment if the watercraft is overturned.
There, however, are several problems associated the emergency shut-off system described above. In particular, the circuit in the overturn switch can close when the watercraft is making a sharp or quick turn. That is, the weight can sway beyond the specified range during a sharp or quick turn as well as when the watercraft is overturned.
Thus, there exists a need for a improve emergency shut-off system that does not suffer significantly from these problems.
Thus, one aspect of the present invention is a method of operating an emergency shut-off system for a small watercraft is disclosed. The small watercraft comprises a hull that defines an engine compartment, an internal combustion engine supported within the engine compartment, an overturn switch, and an electronic control unit that is in electrical communication with the overturn switch. A signal from the overturn switch is sensed by the electronic control unit. The emergency shut-off system determines if the overturn switch is generating a signal for at least a preset amount of time. If the overturn switch has generated a signal for at least the preset amount of time, the engine is shut off.
Another aspect of the present invention is another method of operating an emergency shut-off system for a small watercraft. The small watercraft includes a hull that defines an engine compartment, an internal combustion engine supported within the engine compartment, a water level detection sensor positioned in the engine compartment, a bilge pump, and an electronic control unit that is in electrical communication with the sensor and the pump. The electronic control unit senses a signal from the water level detection sensor. The engine is shut off when the water level detection sensor indicates that water in the engine compartment exceeds a preset level. The bilge pump is activated.
Yet another aspect of the present invention is a small watercraft comprising a hull that defines an engine compartment, an internal combustion engine supported within the engine compartment, and an emergency shut-off system. The emergency shut-off system comprises an overturn switch and an electronic control unit that is in electrical communication with the overturn switch and the engine. The electronic control unit is configured to sense a signal generated by the overturn switch. The electronic control unit is also configured to determine if the signal generated by the overturn switch continues for a period longer than a preset amount of time. The electronic control unit is further configure to shut off the engine if the signal generated by the overturn switch continues beyond the preset amount of time.
Another aspect of the present invention is a small watercraft comprising a hull that defines an engine compartment, an internal combustion engine supported within the engine compartment, a water level detection sensor positioned in the engine compartment, a bilge pump positioned within the hull, and an electronic control unit. The electronic control unit is in electrical communication with the bilge pump and the engine. The sensor is configured to send a signal to the electronic control unit when water in the engine compartment rises above a specified level. The electronic control unit is configured to sense the signal from the water level detection sensor, to shut off the engine and to activate a bilge pump that is positioned within the engine compartment.
Another aspect of the present invention is a small watercraft comprising a hull that defines an engine compartment, an internal combustion engine supported within the engine compartment, a bilge pump positioned within the hull, and an electronic control unit in electrical communication with the bilge pump and the internal combustion engine. The watercraft also includes means for shutting off the engine when the watercraft is overturned.